U.S. patent application number 17/249897 was filed with the patent office on 2022-09-22 for remote visualization apparatus comprising a borescope and methods of use thereof.
The applicant listed for this patent is Southwest Research Institute. Invention is credited to Joseph Nathan MITCHELL, Albert Joseph PARVIN, JR..
Application Number | 20220299645 17/249897 |
Document ID | / |
Family ID | 1000005565759 |
Filed Date | 2022-09-22 |
United States Patent
Application |
20220299645 |
Kind Code |
A1 |
MITCHELL; Joseph Nathan ; et
al. |
September 22, 2022 |
REMOTE VISUALIZATION APPARATUS COMPRISING A BORESCOPE AND METHODS
OF USE THEREOF
Abstract
A remote 3D measurement and visualization apparatus which
comprises a borescope, comprising a shaft; a time-of-flight (TOF)
depth camera having a plurality of pixels; an illumination source
to emit illumination source light; wherein an illumination
transmission portion of the shaft is operatively arranged to
transmit the illumination source light distally along the shaft and
emit the illumination source light from a distal end of the
borescope to illuminate a target volume; wherein an image
transmission portion of the shaft is operatively arranged to
receive reflected illumination source light from the target volume
and transmit the reflected illumination source light proximally
along the shaft to the TOF depth camera; and wherein the TOF depth
camera is operatively arranged to transmit intensity and phase data
of the reflected illumination source light from the pixels to a
processor and/or a computer to generate a digital,
three-dimensional, spatial representation of the target volume.
Inventors: |
MITCHELL; Joseph Nathan;
(San Antonio, TX) ; PARVIN, JR.; Albert Joseph;
(San Antonio, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Southwest Research Institute |
San Antonio |
TX |
US |
|
|
Family ID: |
1000005565759 |
Appl. No.: |
17/249897 |
Filed: |
March 17, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 17/894 20200101;
G02B 23/26 20130101; G02B 23/2469 20130101; G02B 23/2484 20130101;
H04N 13/296 20180501; H04N 13/254 20180501 |
International
Class: |
G01S 17/894 20060101
G01S017/894; G02B 23/24 20060101 G02B023/24; G02B 23/26 20060101
G02B023/26; H04N 13/254 20060101 H04N013/254; H04N 13/296 20060101
H04N013/296 |
Claims
1. A remote 3D measurement and visualization apparatus comprising:
a borescope, comprising a light and image transmission shaft; a
solid state, time-of-flight depth camera having a plurality of
pixels; an illumination source to emit illumination source light;
wherein the illumination source light is modulated or pulsed to
generate a time-varying intensity suitable for the time-of-flight
depth camera to measure distances within a target volume; wherein
the shaft has a diameter suitable to enter the target volume
through an access point; wherein the shaft has an illumination
transmission portion and an image transmission portion; wherein the
illumination transmission portion of the shaft is operatively
arranged to transmit the illumination source light from the
illumination source distally along the shaft and emit the
illumination source light from a distal end of the borescope to
illuminate the target volume; wherein the image transmission
portion of the shaft is operatively arranged to receive reflected
illumination source light from the target volume and transmit the
reflected illumination source light proximally along the shaft to
the time-of-flight depth camera; and wherein the time-of-flight
depth camera is operatively arranged to transmit intensity and
phase data of the reflected illumination source light from the
pixels to a processor and/or a computer to generate a digital,
three-dimensional, spatial representation of the target volume.
2. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the borescope comprises a proximal control unit
coupled to the shaft; and wherein the proximal control unit
comprises the time-of-flight depth camera.
3. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the borescope comprises a proximal control unit
coupled to the shaft; and wherein the proximal control unit
comprises the illumination source.
4. The remote 3D measurement and visualization apparatus according
to claim 1, wherein a camera coupling lens is disposed between a
proximal end of the image transmission portion of the shaft and the
time-of-flight depth camera; and wherein the camera coupling lens
images the reflected illumination source light transmitted from the
image transmission portion of the shaft onto an image plane of the
time-of-flight depth camera.
5. The remote 3D measurement and visualization apparatus according
to claim 1, wherein an illumination source coupling lens is
disposed between a proximal end of the illumination transmission
portion of the shaft and the illumination source; and wherein the
illumination source coupling lens operatively couples the
illumination source light from the illumination source to the
illumination transmission portion of the shaft.
6. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the shaft is a flexible shaft; wherein the
illumination transmission portion of the shaft is provided by a
first group of optical fibers; and wherein the image transmission
portion of the shaft is provided by a second group of optical
fibers.
7. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the shaft is a rigid shaft; and wherein at
least one of the illumination transmission portion of the shaft and
the image transmission portion of the shaft is provided by a rigid
tubular light guide, respectively.
8. The remote 3D measurement and visualization apparatus according
to claim 7, wherein the rigid tubular light guide comprises at
least one rod lens.
9. The remote 3D measurement and visualization apparatus according
to claim 7, wherein the rigid tubular light guide comprises at
least one relay lens.
10. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the illumination source comprises a laser.
11. The remote 3D measurement and visualization apparatus according
to claim 10, wherein the laser is a diode laser.
12. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the illumination source comprises one or more
light emitting diodes.
13. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the image transmission portion of the shaft is
provided by a group of optical fibers; and wherein the group of
optical fibers are arranged in a coherent array so that their
relative positions remain fixed from one end to an opposing end of
the group.
14. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the time-of-flight depth camera comprises an
image or a focal plane having an array of the pixels; wherein the
image transmission portion of the shaft is provided by a group of
optical fibers; wherein each pixel of the array of the pixels is
operatively coupled to one of the optical fibers in a one-to-one
relationship; and wherein a position of each of the optical fibers
remains fixed relative to one another from a proximal end of each
fiber to a distal end of each fiber, respectively.
15. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the diameter of the shaft is 1 mm to 25 mm.
16. The remote 3D measurement and visualization apparatus according
to claim 1, wherein the diameter of the shaft is 8 mm or less.
17. A method of operating a remote 3D measurement and visualization
apparatus comprising: obtaining the remote 3D measurement and
visualization apparatus, wherein the remote visualization apparatus
comprises a borescope, comprising a light and image transmission
shaft; a solid state, time-of-flight depth camera having a
plurality of pixels; an illumination source to emit illumination
source light; wherein the illumination source light is modulated or
pulsed to generate a time-varying intensity suitable for the
time-of-flight depth camera to measure distances within a target
volume; wherein the shaft has a diameter suitable to enter the
target volume through an access point; wherein the shaft has an
illumination transmission portion and an image transmission
portion; wherein the illumination transmission portion of the shaft
is operatively arranged to transmit the illumination source light
from the illumination source distally along the shaft and emit the
illumination source light from a distal end of the borescope to
illuminate a target volume; wherein the image transmission portion
of the shaft is operatively arranged to receive reflected
illumination source light from the target volume and transmit the
reflected illumination source light proximally along the shaft to
the time-of-flight depth camera; and wherein the time-of-flight
depth camera is operatively arranged to transmit intensity and
phase data of the reflected illumination source light from the
pixels to a processor and/or a computer to generate a digital,
three-dimensional, spatial representation of the target volume;
inserting the shaft of the borescope through an access point of a
structure; and operating the remote visualization apparatus,
including the borescope, to generate the digital,
three-dimensional, spatial representation of a target volume within
the structure.
18. The method of operating a remote visualization apparatus 15
wherein operating the remote visualization apparatus is performed
as part of an inspection of the target volume.
Description
FIELD
[0001] The present disclosure relates to borescopes, methods of use
and systems thereof, and, more particularly, such which make use of
light detection and ranging, which may be referred to by the
acronym LIDAR, for 3D visualization and measurement of a volume
through a confined space access point.
BACKGROUND
[0002] Characterization and inspection of industrial equipment,
facilities and other structures must sometimes be carried out
through an access point which may comprise a small port, a confined
space, or a convoluted/tortious path, such as a pipe. In military
applications, soldiers and other combatants must occasionally
assess a space (e.g. room) prior to entry by inserting a probe
under a door or through another small opening into the space to
determine the layout of the space and/or if adversaries are
present. These types of inspections can be carried out by a small
diameter, visual borescope.
[0003] The borescope may contain a bundle of optical fibers that
transmit an image of an inspection site, scene or other target area
to an eyepiece. These borescopes may also provide an illumination
source which provides illumination of the target area via one or
more of the optical fibers in the bundle. However, the view through
these borescopes can sometimes be difficult to interpret (e.g.
distorted), particularly if there are no features present to
provide a sense of scale and the low contrast of borescope images
can mask objects or cause them to have an ambiguous relationship to
their surroundings. In some applications, it may be important to be
able to accurately measure the dimensions of what is being
inspected or otherwise viewed for planning or verification. This
cannot be readily done with a visual borescope.
[0004] One methodology useful for area measurement is LIDAR, which
stands for either "Light Imaging Detection And Ranging" or "LIght
and raDAR". LIDAR is a remote-sensing technology for estimating
distance/range/depth with use of an integrated illumination source,
particularly a laser. More particularly, a laser beam emitted from
the laser is used to illuminate a target volume, and the reflection
of the laser light illumination in the target volume, such as from
objects, is then detected and measured with a sensor, particularly
a photodetector. The remote measurement principle may be referred
to as time-of-flight (TOF).
[0005] To date, solid-state LIDAR has mostly been used in large
area surveying/mapping, e.g. using aircraft, as well as obstacle
avoidance and localization applications such as autonomous motor
vehicles, unmanned aerial vehicles (UAVs), and in machine vision
for industrial robotics. However, LIDAR has not been used through
confined access points associated with use of a borescope.
SUMMARY
[0006] A remote 3D measurement and visualization apparatus which
comprises a borescope, comprising a light and image transmission
shaft; a solid state, time-of-flight depth camera having a
plurality of pixels; an illumination source to emit illumination
source light; wherein the illumination source light is modulated or
pulsed to generate a time-varying intensity suitable for the
time-of-flight depth camera to measure distances within a target
volume; wherein the shaft has a diameter suitable to enter the
target volume through a confined (size-restricted) access point;
wherein the shaft has an illumination transmission portion and an
image transmission portion; wherein the illumination transmission
portion of the shaft is operatively arranged to transmit the
illumination source light from the illumination source distally
along the shaft and emit the illumination source light from a
distal end of the borescope to illuminate the target volume;
wherein the image transmission portion of the shaft is operatively
arranged to receive reflected illumination source light from the
target volume and transmit the reflected illumination source light
proximally along the shaft to the time-of-flight depth camera; and
wherein the time-of-flight depth camera is operatively arranged to
receive the reflected illumination source light from the image
transmission portion of the shaft and to transmit intensity
(amplitude) and phase data of the reflected illumination source
light from the pixels to a processor and/or a computer to generate
a digital, three-dimensional, spatial representation of the target
volume.
[0007] In at least one embodiment, the borescope comprises a
proximal control unit coupled to the shaft; and the proximal
control unit comprises the time-of-flight depth camera.
[0008] In at least one embodiment, the borescope comprises a
proximal control unit coupled to the shaft; and the proximal
control unit comprises the illumination source.
[0009] In at least one embodiment, a camera coupling lens is
disposed between a proximal end of the image transmission portion
of the shaft and the time-of-flight depth camera; and the camera
coupling lens images the reflected illumination source light
transmitted from the image transmission portion of the shaft onto
an image plane of the time-of-flight depth camera.
[0010] In at least one embodiment, an illumination source coupling
lens is disposed between a proximal end of the illumination
transmission portion of the shaft and the illumination source; and
the illumination source coupling lens operatively couples the
illumination source light from the illumination source to the
illumination transmission portion of the shaft.
[0011] In at least one embodiment, the shaft is a flexible shaft;
the illumination transmission portion of the shaft is provided by a
first group of optical fibers; and the image transmission portion
of the shaft is provided by a second group of optical fibers.
[0012] In at least one embodiment, the shaft is a rigid shaft; and
at least one of the illumination transmission portion of the shaft
and the image transmission portion of the shaft is provided by a
rigid tubular light guide, respectively.
[0013] In at least one embodiment, the rigid tubular light guide
comprises at least one rod lens.
[0014] In at least one embodiment, the rigid tubular light guide
comprises at least one relay lens.
[0015] In at least one embodiment, the illumination source
comprises a laser.
[0016] In at least one embodiment, the laser is a diode laser.
[0017] In at least one embodiment, the illumination source
comprises one or more light emitting diodes.
[0018] In at least one embodiment, the image transmission portion
of the shaft is provided by a group of optical fibers; and the
group of optical fibers are arranged in a coherent array so that
their relative positions remain fixed from one end to an opposing
end of the group.
[0019] In at least one embodiment, the time-of-flight depth camera
comprises an image or a focal plane having an array of the pixels;
the image transmission portion of the shaft is provided by a group
of optical fibers; each pixel of the array of the pixels is
operatively coupled to one of the optical fibers in a one-to-one
relationship; and a position of each of the optical fibers remains
fixed relative to one another from a proximal end of each fiber to
a distal end of each fiber, respectively.
[0020] In at least one embodiment, the diameter of the shaft is 1
mm to 25 mm.
[0021] In at least one embodiment, the diameter of the shaft is 8
mm or less.
[0022] A method of operating a remote 3D measurement and
visualization apparatus which comprises obtaining the remote 3D
measurement and visualization apparatus, wherein the remote
visualization apparatus comprises a borescope, comprising a light
and image transmission shaft; a solid state, time-of-flight depth
camera having a plurality of pixels; an illumination source to emit
illumination source light; wherein the illumination source light is
modulated or pulsed to generate a time-varying intensity suitable
for the time-of-flight depth camera to measure distances within a
target volume; wherein the shaft has a diameter suitable to enter
the target volume through an access point; wherein the shaft has an
illumination transmission portion and an image transmission
portion; wherein the illumination transmission portion of the shaft
is operatively arranged to transmit the illumination source light
from the illumination source distally along the shaft and emit the
illumination source light from a distal end of the borescope to
illuminate a target volume; wherein the image transmission portion
of the shaft is operatively arranged to receive reflected
illumination source light from the target volume and transmit the
reflected illumination source light proximally along the shaft to
the time-of-flight depth camera; and wherein the time-of-flight
depth camera is operatively arranged to transmit intensity and
phase data of the reflected illumination source light from the
pixels to a processor and/or a computer to generate a digital,
three-dimensional, spatial representation of the target volume;
inserting the shaft of the borescope through an access point of a
structure; and operating the remote visualization apparatus,
including the borescope, to generate the digital,
three-dimensional, spatial representation of a target volume within
the structure.
[0023] In at least one embodiment, operating the remote
visualization apparatus is performed as part of an inspection of
the target volume.
FIGURES
[0024] The above-mentioned and other features of this disclosure,
and the manner of attaining them, will become more apparent and
better understood by reference to the following description of
embodiments described herein taken in conjunction with the
accompanying drawings, wherein:
[0025] FIG. 1 is a perspective view of a remote visualization
apparatus, comprising a borescope, according to the present
disclosure;
[0026] FIG. 2 is a side view of portions of the remote
visualization apparatus of FIG. 1; and
[0027] FIG. 3 is a perspective view of a rigid tubular light guide
for a remote visualization apparatus.
DETAILED DESCRIPTION
[0028] It may be appreciated that the present disclosure is not
limited in its application to the details of construction and the
arrangement of components set forth in the following description or
illustrated in the drawings. The invention(s) herein may be capable
of other embodiments and of being practiced or being carried out in
various ways. Also, it may be appreciated that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting as such may be understood by one
of skill in the art.
[0029] Referring now to FIGS. 1-2, there is shown a remote 3D
measurement and visualization LIDAR apparatus 2, particularly
comprising a borescope 10. The LIDAR apparatus 2, borescope 10 and
accompanying methods of use thereof may provide a solution for
remotely measuring distance/range/depth of a target volume 100,
particularly within, inside, defined by or otherwise formed by a
structure 102, through a small, confined, access point 110,
particularly by combining the imaging capabilities of an elongated
light and image transmission shaft 12, which may comprise a bundle
of optical fibers 50 (as shown in FIG. 2 where the outer sheath 48
of the shaft 12 has been removed), with a (TOF) solid-state camera
20 and an illumination source 30. The remote measurement may then
be used to generate a contour (i.e. topographical) map/survey,
particularly in a form of a digital (visual), three-dimensional,
spatial representation of the target volume 100 with the objects
therein.
[0030] The structure 102, which may be any man-made structure (e.g.
building, machine or other device), natural structure (e.g. cave)
or a combination thereof. Structure 102 may include an enclosing
structure, particularly a substantially enclosed structure such
that the area of all openings into the target volume 100 is 25% or
less of the area of the structure defining the target volume 100).
The access point 110 may be an opening in the structure 102, such
as an opening in floor, roof or wall of the structure 102, an
opening beneath a door or window of the structure 102, an opening
provided by a ventilation passage of the structure 102). The
opening may have an exemplary area of 100 sqcm. (square
centimeters) or less (e.g. 0.01 sqcm. to 100 sqcm.; 0.01 sqcm. to
50 sqcm.; 0.01 sqcm. to 25 sqcm.; 0.01 sqcm. to 10 sqcm; 0.01 sqcm.
to 5 sqcm.)
[0031] As shown, borescope 10 may comprise the light and image
transmission shaft 12 and a proximal control unit 14. The camera 20
may be provided as part of the borescope 10 (e.g. control unit 14)
or otherwise part of the LIDAR apparatus 2. As set forth above,
camera 20 may more particularly be a solid-state camera. A solid
state camera may be understood to use a solid-state (digital) image
sensor. The digital image sensor is an image sensing device that
detects (senses) incoming light (photons), corresponding to a
target volume 100 (e.g. optical image) via the field of view, and
converts the light into electrical (electronic digital)
signals.
[0032] In general terms, the digital image sensor is an integrated
circuit chip which has an array of light sensitive components on a
surface, which may be the image plane or the focal plane. The array
is formed by individual photosensitive sensor elements. Each
photosensitive sensor element converts light detected thereby to an
electrical signal. The full set of electrical signals are then
converted into an image by an on-board processor or computer
processor (i.e. integrated with the chip).
[0033] More specifically, the digital image sensor detects the
light, converts the light into electrical signals and then
transmits the electrical signals to the computer processor, which
transforms the electronic signals into a two-dimensional (2D) or
three-dimensional (3D) digital representation of the target volume
100 (e.g. a digital image that can be viewed on an image screen,
analyzed, or stored).
[0034] As known in the art, the image sensor may more particularly
perform photoelectric conversion (i.e. convert photons into
electrons, with the number of electrons being proportional to the
intensity of the light); charge accumulation (i.e. collect
generated charge as signal charge); transfer signal (i.e. move
signal charge to detecting node); signal detection (i.e. convert
signal charge into electrical signal (voltage)); and analog to
digital conversion (i.e. convert voltage into digital value).
[0035] More particularly, the image sensor may be an active-pixel
sensor (APS), in which the individual photosensitive sensor
elements comprises a plurality of pixel sensor unit cells, in which
each pixel sensor unit cell has a photodetector, e.g. a pinned
photodiode and one or more active transistors. An exemplary
active-pixel sensor may be a metal-oxide semiconductor active-pixel
sensor (MOS APS), which uses metal-oxide semiconductor field-effect
transistors (MOSFETs) as amplifiers. Even more particularly, the
active-pixel sensor may be a complementary metal-oxide
semiconductor active-pixel sensor (CMOS APS). The photodiode may be
an avalanche photodiode (APD), such as a Geiger-mode avalanche
photodiode (G-APD), and may be particularly based on the
indium-gallium-arsenide-phosphide (InGaAsP) material system.
[0036] In addition to comprising a photodiode, each pixel sensor
unit cell may comprise a micro lens which guides light into the
photodiode. Thus, it may be understood that each pixel sensor unit
cell may have a photodiode and a micro lens in one-to-one
relationship.
[0037] The plurality of pixel sensor unit cells, each of which may
simply be referred to as a pixel (short for picture element), are
arranged in an array of horizontal rows and vertical columns. Thus,
the pixels may be referred to as a pixel array, the micro lenses
may be referred to as a micro lens array and the photodiodes may be
referred to as a photodiode array. Furthermore, it should be
understood that the number of pixels will define the camera
resolution.
[0038] The image sensor may be a visible light sensor, or an
infrared light sensor. The visible light sensor may be either a
mono sensor (to produce a monochrome image) or a color sensor (to
produce a color image). If the image sensor is a color image
sensor, each pixel will further comprise a color filter disposed
between the micro lens and photodiode, respectively, which may be
referred to as a color filer array.
[0039] In order to generate an array of depth measurements, the
solid-state camera 20 may more particularly be a time-of-flight
(TOF) depth camera 20. With a TOF depth camera 20, rather than
measuring ambient light, the TOF depth camera 20 measures reflected
light of the illumination source 30, which also may be referred to
as a light source emitter, which is reflected as discussed in
greater detail below. Incident light 32 coming from the
illumination source 30 is diverged such that target volume 100 is
illuminated, and the reflected light of the illumination source 30
is imaged onto a two-dimensional array of photodetectors. In making
reference to a TOF depth camera 20, it should be understood that
such is not a range scanner (e.g. rotating mirror), and hence the
TOF depth camera 20 may be considered to be a scannerless
device.
[0040] TOF measurement may be performed a few different ways,
depending on the TOF depth camera 20. Depending on how TOF
measurement is performed, the TOF depth camera 20 may further be
referred to as a pulsed-light (or Direct Time-of-Flight) camera, or
a continuous-wave modulated light camera. With a pulsed-light
camera, the illumination source 30 may emit pulsed laser light, and
differences in the directly measured return times and wavelengths
of the laser light to the image sensor may then be used to provide
a topographical survey/map of the target volume 100. Alternatively,
with a continuous-wave modulated light camera, a phase difference
between the emitted and received laser light signals is measured to
provide an indirect measurement of travel time. Another TOF
measurement technique is referred to as range-gating and uses a
shutter (either mechanical or electronic) that opens briefly in
synchronization with the outgoing light pulses. Only a portion of
the reflected light pulse is collected during the interval the
shutter is open and its intensity provides an indirect measurement
of distance.
[0041] Accordingly, with a pulsed-light camera, the image sensor
may be referred to as a pulsed light sensor, or more particularly a
pulsed laser light sensor, which directly measures the round-trip
time of a light pulse (e.g. a few nanoseconds). Once the pulsed
light is reflected on an object, the light pulses are detected by
the array of photodiodes that are combined with time-to-digital
converters (TDCs) or with time-to-amplitude circuitry. The pulsed
light photodetectors may be single photon avalanche diodes. With a
3D flash LIDAR TOF depth camera, the illumination source 30 may be
provided from a single laser to illuminate the target volume 100. A
1-D or 2-D array of photodetectors is then used to obtain a depth
image.
[0042] With a continuous-wave modulated light camera, the image
sensor may be referred to as a continuous-wave modulation sensor,
which measures the phase differences, particularly between an
emitted continuous sinusoidal light-wave signal and the
backscattered signals received by each photodetector. The phase
difference is then correlated related to distance. With a
range-gated camera, the image sensor may be referred to as a
range-gated sensor, which measures the intensity of the reflected
light pulse over an interval of time shorter than the duration of
the light pulse. The intensity of the pulse on a pixel is used to
determine the distance to that point.
[0043] As set forth above, the borescope 10 further comprises an
illumination source 30, particularly a laser which emits laser
light. As with the TOF depth camera 20, the illumination source 30
may be provided as part of the borescope 10 (e.g. control unit 14)
or otherwise part of the LIDAR apparatus 2. All of the solid-state
LIDAR techniques for use with the present disclosure require a
high-speed illumination source 30, with an irradiance in the target
volume sufficient to overcome the background light, such as a laser
or LED. The rise time of the light source may need to be as short
as a few nanoseconds for a pulsed light sensor but could be as long
as a hundred nanoseconds for a continuous wave modulated
sensor.
[0044] Depending on the LIDAR technique, the incident light 32 may
be amplitude modulated or one or more pulses. In either case, the
modulation frequency must be high speed (tens of megahertz) or the
pulses must be of very short duration (usually less than 10
nanoseconds).
[0045] High intensity is needed to provide a sufficiently strong
reflection from surfaces of the target volume 100 for the TOF depth
camera 20 to obtain a signal strong enough to overcome the ambient
background light. Solid state illumination sources, such as a laser
and some LEDs can provide a high enough intensity and fast enough
modulation to meet the requirements for use with a solid-state, TOF
depth camera 20.
[0046] The intensity for the illumination source 30 for the LIDAR
apparatus 2/borescope 10 of the present disclosure is greater than
those which may be employed for other LIDAR applications, in part
to offset the inefficiencies associated with the optical fiber
bundle 50 but also due to the need to spread the light over a large
area that covers the image sensor field of view.
[0047] FIG. 1 shows illumination source 30 as a diode laser, which
is the most common type of laser capable of high-speed modulation,
but other types of lasers may also be employed. Although
near-infrared is the most common wavelength used with TOF depth
camera 20, any wavelength within the sensitivity range of the TOF
depth camera 20 and the transmission band of the optical fiber
bundle 50 of the LIDAR apparatus 2/borescope 10 can be employed.
Illumination source 30 may be operatively coupled to a
radio-frequency (RF) modulator 40 via a cable 42. Alternatively,
the radio-frequency (RF) modulator 40 may be provided as part of
the borescope 10 (e.g. control unit 14).
[0048] As set forth above, the LIDAR apparatus 2/borescope 10
further comprises an optical fiber bundle 50. The optical fiber
bundle 50 uses an array of fibers arranged coherently, so that
their relative positions remain fixed from end to end of the
optical fiber bundle 50. The number of fibers determines the
spatial resolution of the apparatus and can range from 10,000
fibers to 1,000,000 fibers. Exemplary resolutions may include
320.times.240, 640.times.480 and 1280.times.720. The optical fiber
bundle 50 is flexible and may have a length in a range of 1 to 3
meters. Given the flexibility, the optical fiber bundle 50 may be
used with a flexible borescope, however such flexibility does not
preclude use in a rigid borescope, which commonly employ either a
rod lens or a set of relay lenses instead of optical fibers.
[0049] The optical fiber bundle 50 may be operatively coupled
between a distal optic 60 and a proximal optic 70 of the borescope
10. As shown, the distal optic 60 forms a distal end 62 of the
borescope 10/shaft 12, and is disposed adjacent a distal end region
52 of the optical fiber bundle 50, particularly to illuminate and
image the target volume 100 via the field of view. Proximal optic
70 is disposed adjacent a proximal end region 54 of the optical
fiber bundle 50, particularly to operatively couple the
illumination source 30 and the TOF depth camera 20 to the optical
fiber bundle 50, and electronics to synchronize and control TOF
depth camera 20 and the illumination source 30.
[0050] More particularly, the proximal optic 70 may comprise an
illumination source (fiber) coupling lens 72 which operatively
couples the illumination source 30 to an illumination fiber
sub-group 56 of the optical fiber bundle 50, and a camera coupling
(imaging) lens 74 which operatively couples the TOF depth camera 20
to an image fiber sub-group 58 of the optical fiber bundle 50.
[0051] As shown, the illumination source (fiber) coupling lens 72
and the camera coupling lens 74 are operatively coupled to the
respective illumination fiber sub-group 56 and the image fiber
sub-group 58, respectively, via an optical fiber bundle interface
80, which joins the illumination fiber sub-group 56 and the image
fiber sub-group 58 into the optical fiber bundle 50 as such extends
distally.
[0052] As shown, the optical fiber bundle interface 80 is disposed
adjacent the proximal end region 54 of the optical fiber bundle 50.
Also as shown, the illumination source (fiber) coupling lens 72 is
disposed between the illumination source 30 and the optical fiber
bundle interface 80. Similarly, the camera coupling (imaging) lens
74 is disposed between the TOF depth camera 20 and the optical
fiber bundle interface 80.
[0053] As may be understood from the foregoing arrangement, the
incident light 32 from the illumination source 30 is directed to
illumination source (fiber) coupling lens 72, which directs the
incident light 32 into the proximal ends of the illumination fiber
sub-group of the optical fiber bundle 50. Illumination source
(fiber) coupling lens 72 is used to efficiently couple the maximum
amount of light from the illumination source 30 into the
illumination fiber sub-group of the optical fiber bundle 50.
[0054] The incident light 32 travels through the fibers of the
illumination fiber sub-group 56 of the optical fiber bundle 50 to
the distal end of the fibers, where it exits the fibers at the
distal optic 60. After being reflected after contacting surfaces in
the target volume 100, the reflected light (from the illumination
source 30) enters the distal ends of the optical fibers of the
image fiber sub-group 58 of the optical fiber bundle 50 through the
distal optic 60, which may comprise a small imaging lens 66 (such
those used with cameras) which collects light from the target
volume 100 and focuses it onto the image fiber sub-group 58 of the
optical fiber bundle 50 for transmission. The reflected light then
travels proximally to the imaging lens 74 and thereafter to the
image sensor of the TOF depth camera 20. The imaging lens 74 images
the proximal end of the image fiber sub-group 58 of the optical
fiber bundle 50 onto the image plane of the TOF depth camera
20.
[0055] It should be understood that, with the optical fiber bundle
50, the incident light 32 from the illumination source 30 is
transmitted out through the fibers of the illumination fiber
sub-group 56 and thereafter reflected back through the image fiber
sub-group 58 (as reflected light from the illumination source 30),
and that the illumination fiber sub-group 56 and the image fiber
sub-group 58 separate at the optical fiber bundle interface 80 so
that the incident light 32 does not directly (i.e. without
reflection) reach the TOF depth camera 20. More particularly, the
incident light output of the illumination fiber sub-group is not
through the imaging lens of the distal optic 60, to avoid
back-reflections to the TOF camera 20.
[0056] Each optical fiber of the image fiber sub-group 58 of the
optical fiber bundle 50 is coupled to a particular pixel of the
pixel array of the TOF depth camera 20 in a one-to-one
relationship, and the fibers are arranged coherently, so that their
relative positions remain fixed from the proximal end/TOF camera 20
to the distal end.
[0057] Other electronics may be used to control the TOF camera 20
and illumination source 30, particularly to synchronize the laser
modulation or pulses with the camera's frame acquisition. While
FIG. 1 shows an RF modulator 40, which would be used for a
phase-shift detection technique, but a pulse generator would be
used with a direct TOF approach. A constant current controller and
thermoelectric cooling controller may also be required to properly
drive the illumination source 30. A separate computer 90 (e.g.
laptop) can be used for data collection from the TOF depth camera
20, but integrated data collection electronics may also be
employed.
[0058] The elongated shaft 12 of the borescope 10, which comprises
the distal end region 52 of the optical fiber bundle 50 and the
distal optic 60, has a diameter which may be sized for the
application and/or the access point. For example, for small
inspection applications and/or small access points and/or where
detection of the boroscope is undesirable (e.g. by an adversary or
otherwise), the diameter may be 8 mm or less (e.g. 1 mm to 8 mm)
and more particularly 6 mm or less (e.g. 1 mm to 6 mm), In other
applications where the size of the access point may be larger
and/or detection of the boroscope is not a concern, the diameter
may be larger, e.g. 9 mm to 25 mm to allow more light to be
collected. Thus, it should be understood that the diameter may be
in a range of 1 mm to 25 mm. The optical fiber bundle 50 is
flexible. One illumination configuration arranges the illumination
fiber sub-group 56 in an annular ring 64 around the perimeter of
the distal end to evenly spread the incident light. The center of
the annual ring of illumination fibers is occupied by the image
fiber subgroup 58. The solid-state TOF depth camera 20 uses a phase
detection approach, as this is lower in cost and provides good
range and resolution while not having the strict short pulse
requirements of the direct TOF approach. A near-infrared diode
laser provides a low cost compact illumination source 30 that best
matches the sensitivity range of the TOF depth camera 20.
[0059] Referring to FIG. 3, in another embodiment, for a rigid
borescope, at least one of the illumination fiber sub-group of the
optical fiber bundle 50 and the reflection fiber sub-group of the
optical fiber bundle 50 are replaced with a rigid (glass or
plastic) tubular light guide 92, which may comprise one or more rod
lenses and/or relay lenses, respectively. The rigid borescope may
have a length of 0.25 meters to 1 meter.
[0060] The TOF camera pixels output amplitude and phase information
that the camera uses to generate a distance measurement for each
pixel. The intensity and distance information is sent to a
processor or computer 90 for visualization and further processing.
The computer or processor 90 can use the distance information for
each pixel and the field of view of the camera to compute a 3D
point cloud of the target volume 100 allowing the position of
objects within it to be determined.
[0061] While a preferred embodiment of the present invention(s) has
been described, it should be understood that various changes,
adaptations and modifications can be made therein without departing
from the spirit of the invention(s) and the scope of the appended
claims. The scope of the invention(s) should, therefore, be
determined not with reference to the above description, but instead
should be determined with reference to the appended claims along
with their full scope of equivalents. Furthermore, it should be
understood that the appended claims do not necessarily comprise the
broadest scope of the invention(s) which the applicant is entitled
to claim, or the only manner(s) in which the invention(s) may be
claimed, or that all recited features are necessary.
LIST OF REFERENCE CHARACTERS
[0062] 2 remote visualization LIDAR apparatus [0063] 10 borescope
[0064] 12 elongated (light and image transmission) shaft [0065] 14
proximal control unit [0066] 20 (TOF) depth camera [0067] 30
illumination source [0068] 32 incident light [0069] 40
radio-frequency modulator and laser controller [0070] 42 laser
controller cable [0071] 48 sheath of shaft [0072] 50 optical fiber
bundle [0073] 52 distal end region of the optical fiber bundle
[0074] 54 proximal end region of the optical fiber bundle [0075] 56
illumination fiber sub-group of optical bundle (illumination
transmission portion of shaft) [0076] 58 image fiber sub-group of
optical bundle (image transmission portion of shaft) [0077] 60
distal optic [0078] 62 distal end of borescope/shaft [0079] 64
annular ring [0080] 66 imaging lens [0081] 70 proximal optic [0082]
72 illumination source (fiber) coupling lens [0083] 74 camera
coupling (imaging) lens [0084] 80 optical fiber bundle interface
[0085] 90 processor or computer [0086] 92 rigid tubular light guide
[0087] 100 target volume [0088] 102 structure [0089] 110 confined
space access point
* * * * *